Study on the enhancement of physical properties of coral aggregates through superfine cement paste suction under negative pressure

In marine civil engineering, the pore characteristics and mechanical properties of coral aggregates limit their application in construction engineering. This paper experimentally explored a paste suction technology aimed at enhancing the physical properties of coral aggregate. This study initially prepared superfine cement paste, which was used to be suctioned into the coral pores by negative pressure. Subsequently, the crush resistance, density, porosity, permeability resistance, and microstructures of coral aggregate were investigated before and after paste suction. The study found that this technology enabled the suction of superfine cement paste into the coral pores, thereby reducing the porosity of the coral and significantly enhancing the mechanical properties and permeability resistance of the coral aggregate. To ensure the optimal enhancement effect on the coral, the prepared paste needed to prioritize ensuring fluidity before increasing mechanical strength. However, when the fluidity reached the threshold, further increasing the strength of the paste resulted in a more pronounced improvement in the physical properties of the coral aggregate. The improvement of coral permeability resistance could be achieved through two approaches: either by increasing the thickness and compactness of the paste coating the outer surface of the coral, or by enhancing the amount and compactness of the paste suctioned into the internal pores of the coral. Microscopic experiments further revealed that coral exhibits three types of pore structures. Coral with well-connected and uniformly distributed pores demonstrated the most significant performance improvement due to paste suction, whereas coral with a large number of closed pores and micropores exhibited limited enhancement effects. However, for coral concrete applications, the paste suction technology was feasible and effective in enhancing the mechanical properties and permeability resistance of coral aggregate.